A few days ago I tried to make backup DVDs using Dell DataSafe Local Backup software. It wouldn't write the discs. Then I tried to burn another .ISO file using the software provided by dell, it appeared as if the DVD was burnt successfully, however when I checked the disc it was empty. I tried DVD-R from a different vendor, but the same result. Kindly help me what should I do.

Please click Osprey's Toolbox (link below) and find the link to DVD Identifier. Run that program with a blank DVD disc in the drive and tell me what manufacturer and media code are reported by the program.

Well, neither of these is what I would consider high quality media, but certainly between the two of them, one should work.

I'm almost ready to have you call Dell, but I want to try one more thing. Please click the link below to run the upper and lower filter trick. This will lead you to an MS page with one of those Fit It buttons. Try that and let me know what happened. The utility will tell you whether there is any problem, and also whether it was able to fix the problem.